1. Field of the Invention
The present invention relates to a plate heat exchanger comprising alternately arranged plates compressed together to a pack, forming closed channels by means of gaskets arranged between the plates, alternately for a heat emitting and a heat absorbing medium. These channels may be supplied with the respective medium through entry and exit openings in the plates aligned with each other, profiles extending from the entry and exit openings, and in the region of these profiles, gaskets for separating the entry and exit openings, respectively, from the heat exchanger surfaces are arranged alternately between pairs of plates.
2. Discussion of the Background
The gaskets of plate heat exchangers of this type are usually arranged in flat gasket grooves supporting the gasket laterally. In a known way, the intake and outlet region of the entry and exit openings on the heat exchanger surfaces as such form the weakest points of the gasket. In this region, a gasket is arranged only in every second channel while the heat transferring medium encountering the adjacent plate flows in each interposed channel, the gasket groove forming an undesired flow resistance. In the region under-flowed in this way, the gasket groove bottom does not obtain a sufficient metallic support. Since it is also flat and not embossed in the conventional way, it may deform plastically and elastically, locally reducing the gasket pressure. The reduced gasket pressure results in that a leakage may occur in this region even at lower pressures of the heat exchange medium as well as in other regions of the gasket.
From the state of the art, structures and measures, respectively, for mitigating or reducing the leakiness in the flow region of the entry and exit openings of the plate are known. A known measure consists in partially enlarging the gasket in this region. However, this possibility is limited, since a plastic deformation of the gasket groove bottom still will occur.
Another solution is disclosed in DE-AS-23 09 743. Here a lateral support of the gasket groove bottom is obtained by a suitable embossment.
The patent document DE 32 39 004 C2 discloses another solution approach. Here the gasket groove bottom is reinforced by additional embossments.
The solution according to GB-PS 1 020 045 goes further than the solutions mentioned above, in that the embossments of the gasket groove bottom is metallically supported by the respective following plate, however, without adapting the form of the gasket to the embossment. In GB 2 128 726 A, a gasket is also fillingly adapted to the embossment.
With this state of the art, the problem of the tightness in the outlet region of the entry and exit openings is solved in a satisfactory manner. However, in all these solutions the known gasket groove remains in its basic form and the advantage of the direct support is traded against a reduction of the flow cross-section for the entering and exiting medium.